Tanya C. O'Neill


Tanya C. O’Neill has focused exclusively on environmental law for over 20 years. Her current practice focuses on representation of over a dozen  environmental trustees with regard to environmental bankruptcy trusts with sites in more than 15 different states, both pre-effective date negotiations and due diligence and post confirmation management, remediation, property disposition and conflict resolution.  While the majority of the environmental trust clients own former chemical manufacturing sites, other trusts own properties such as former mines and disposal sites.  Tanya also has significant experience with environmental due diligence related to mergers, acquisitions and multi-state transactions; obtaining and negotiating insurance coverage for environmental contamination and insurance recovery on current and historic policies; and environmental permitting, compliance and remediation. She is a partner in the firm’s Environmental Regulation and Insurance & Reinsurance Litigation Practices.

Tanya regularly counsels sellers, buyers and related corporate counsel throughout the country regarding all aspects of environmental due diligence and related purchase and sale agreement negotiations, and liability allocation. She has been involved in the remediation of sites in more than 25 states, ranging from dry cleaners to mining operations, chemical and pesticide manufacturers to smelters and hazardous and radioactive waste disposal sites.



  • Environmental Law Section of the Wisconsin Bar
  • Milwaukee Bar Association
  • Federation of Environmental Technologists
  • Natural Resources and Insurance Coverage Sections of the American Bar Association